Digital video involves the sensing of light rays emitted from objects within a scene by an image sensor, such as a complementary metal oxide semiconductor (CMOS) sensor. Individual images captured by the image sensor form video frames of a video clip. Each video frame is formed of thousands of individual pixels defined by color and intensity data generated by the image sensor.
Difficulties arise when attempting to capture video images under low light conditions. Often, the images are underexposed as a result of not exposing the image sensor to sufficient amounts of light. The small amount of light being sensed by the image sensor produces a low image signal (i.e., video frames having pixels with low intensities). Unlike during good light conditions where the image signal is strong (high pixel intensities), the noise of the image sensor under low light conditions becomes relatively large compared to the low image signal. As a result, the underexposed images generally have low signal-to-noise ratios (SNR). Such low SNR images are generally low quality images that often appear grainy.
Underexposure may be corrected by increasing the size of the image sensor, but sensor cost increases with size.
Underexposure can also be somewhat corrected by exposing the image sensor for a longer period, for example, by using a lower shutter speed. The longer exposure time allows the sensor to capture more light and, thus, increase the image signal. However, lower shutter speeds often result the blurring of images in the video frames caused by the movement of the camera while capturing a scene of still objects, or capturing moving objects within the scene.
The discussion above is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter.